What is the test for failing to give a jury a unanimous verdict in a sexual assault case?

The failure to provide a unanimity instruction is subject to harmless error analysis under the Chapman standard. "`Where the record provides no rational basis, by way of argument or evidence, for the jury to distinguish between the various acts, and the jury must have believed beyond a reasonable doubt that defendant committed all acts if he committed any, the failure to give a unanimity instruction is harmless. [Citation.] Where the record indicates the jury resolved the basic credibility dispute against the defendant and therefore would have convicted him of any of the various offenses shown by the evidence, the failure to give the unanimity instruction is harmless. [Citation.]'" (People v. Curry, supra, 158 Cal.App.4th at p. 783.)